1. Field of The Invention
The present invention relates generally to a method of manufacturing shutters for floppy disc cartridges or the like. Specifically, the present invention relates to a shutter manufacturing method in which
2. Description of The Related Art
Floppy discs, cassette cartridges and other types of cartridge-contained products utilize a shutter portion, generally made of metal, to cover an access opening of the cartridge when the cartridge is not in use.
Generally, such shutters are pressed from a roll of stainless steel plate. The stainless steel roll is pulled in a feeding direction and processed by a multistage (for example, process steps a-d) process including, for example, a punching step, cutting step, and so forth, to produce a plurality of shutters.
Referring to FIGS. 6(A), (B), a series of shutters prepared from a single sheet of stainless steel plate 2 according to such a conventional process is shown. In the drawing, successive shutter blanks 13a-d are shown in different stages of processing. As may be seen, in step a, a pilot hole 10 and a slide hook opening 11 are formed in the steel plate 2. In step b, a shutter spring hook opening 12 is formed. Then, in step c, the shape of the shutter blank 13 is cut and a remaining connecting portion 14 is formed between the successively formed shutters on tile steel plate 2 and, in step d, shutter access openings 15, 15 are formed.
Then, a first step a of bending processing is performed such that protruding portions of the slide hook opening 11 and the shutter spring hook opening 12 are bent so as to form a slide hook 16 and a shutter spring hook 17 and a protruding portion of the shutter access opening 15 is also bent. Then in a step b of bending processing, the shutter blank 13 is bent into the final shape of the shutter 6, that is, approximately a reverse C-shape. Finally, the connecting portion 14 is removed from between the shutters 6 formed continuously along the steel plate 2 and the process is complete.
However, according to such a process as set forth above, the connecting portion 14 is subject to a large amount of stress during movement of the steel plate 2 in the feeding direction, which may cause the connecting portion to bend as shown in FIG. 7, for example. According to this phenomenon, it is not possible to significantly raise a processing speed of a manufacturing line. Also, a thickness of the steel plate 2 used for manufacturing cannot be reduced.
Also, the shutters may be formed by such a method in which, after the shutter blanks 13 and connecting portions 14 are formed, the fully processed steel plate 2 is moved to another location for bending processing by a method in which a bending member is aligned continuously along a center line of the steel plate 2, corresponding to the position of the connecting members 14 for bending a plurality of shutter blanks into finished shutters 6 in a single step. However, according to this type of processing, the same problems as mentioned above are encountered.
Thus, the present invention is proposed to increase strength and durability of the connecting portion to allow shutters to be processed at a faster speed using thinner materials.